The long-term objective of this research is the identification of specific genetic variants which confer risk for the development of COPD in smokers. This will be achieved by means of fine mapping of the loci identified in objectives 3-4 above, or in a subsequent genome scan involving the 400 sibling pairs; identification of novel genetic variants at these loci; and assessment of the functional significance of these variants and their relation to COPD in an independent sample of subjects.